1. Field of the Invention
The present invention relates to a film deposition apparatus and a film deposition method for depositing, for example, a metal film.
2. Information of the Related Art
In a conventional process for manufacturing a semiconductor integrated circuit, a metal or metallic compound, such as W (tungsten), WSi (tungsten silicide), Ti (titanium), TiN (titanium nitride), or TiSi (titanium silicide), is deposited to form a film on the surface of a semiconductor wafer, as an object to be processed, in order to form a wiring pattern on the wafer surface or fill up indentations between wires and the like.
There are three known methods for depositing metal films of this type, H.sub.2 (hydrogen) reduction method, SiH.sub.4 (silane) reduction method, and SiH.sub.2 Cl.sub.2 (dichlorosilane) reduction method. The SiH.sub.2 Cl.sub.2 reduction method is a method in which a W or WSi film for a wiring pattern is deposited at a high temperature of about 600.degree. C. by using dichlorosilane as a reducing gas. The SiH.sub.4 reduction method is a method in which a W or WSi film for a wiring pattern is deposited at a lower temperature of about 370 to 400.degree. C. by using silane as a reducing gas.
Further, the H.sub.2 reduction method is a method in which a W film for filling up indentations or the like between interconnections on the wafer surface is deposited at a temperature of about 400 to 430.degree. C. by using hydrogen as a reducing gas.
For example, WF.sub.6 (tungsten hexafluoride) is used in any of the methods described above.
FIG. 4 shows a conventional film deposition apparatus for depositing a metal film. A thin table 4 formed of a carbon material or aluminum compound is arranged in a cylindrical process chamber 2 formed of aluminum or the like. Heater 8, e.g., halogen lamps, is located under the table 4 with a diathermanous window 6 of quartz between them.
Heat rays emitted from the heater 8 are transmitted through the diathermanous window 6, and reach and heat the table 4, thereby indirectly heating to and keeping a semiconductor wafer W on the table at a predetermined temperature. At the same time, a process gas, e.g., WF.sub.6 or SiH.sub.4, is fed equally onto the wafer surface from a shower head 10 which is located over the table 4, whereupon a metal film of W or Wsi is deposited on the wafer surface.
In this case, the metal film is deposited not only on the wafer surface, but also on structures in the process chamber, e.g., the chamber wall, shower head surface, and clamp ring (not shown) and other members surrounding the wafer. If the resulting deposited film is separated, it is reduced to particles and causes reduction in the yield of wafer production. To avoid this, the deposit film of extra W or WSi adhering to the surfaces of the internal structures is removed by introducing ClF.sub.3 as a cleaning gas after the process of every predetermined number of wafers, e.g., 25 wafers.
As the wafers are carried into or from the process chamber, a small quantity of water gets into the chamber. Oxygen generated by the resolution of the entrapped water reacts with tungsten to form an oxide. Thereupon, the oxide adheres to the bottom face of shower head 10 which is exposed to a specially high temperature.
This tungsten oxide is a stable substance which cannot be thoroughly removed by the ClF.sub.3 gas which is used in dry cleaning. It is necessary, therefore, to disassemble the whole apparatus and carry out wet cleaning after the process of, for example, every 1,000 wafers. Thus, the frequency of such an elaborate maintenance operation is increased, so that the operating efficiency of the apparatus is lowered substantially.
Disclosed in Japanese Patent Laid-open Publication (Kokai) No. 3-29324 is a plate which has good adhesion to a metal film and the like, and is attached to the inner wall of a process chamber, whereby the maintenance operation is eased. However, this plate is formed of a metal, such as stainless steel, and positively captures a deposit film which produces particles, thus failing to be a very effective measure to solve the problem.